''Aldabrachelys grandidieri'', or Grandidier's giant tortoise, is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

species of

tortoise Tortoises ( ) are reptiles of the family Testudinidae of the order Testudines (Latin for "tortoise"). Like other turtles, tortoises have a shell to protect from predation and other threats. The shell in tortoises is generally hard, and like o ...

that was

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...

Mitochondrial DNA Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondrion, mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the D ...

extracted from

subfossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

bone confirm that it is a distinct species.

Description

''Aldabrachelys grandidieri'' was a giant tortoise, one of the largest in the world, measuring about in carapace length. It was originally one of the six endemic

species of Madagascar (two large '' Aldabrachelys''; two medium '' Astrochelys''; two small ''

Pyxis Pyxis is a small and faint constellation in the southern sky. Abbreviated from Pyxis Nautica, its name is Latin for a mariner's compass (contrasting with Circinus, which represents a draftsman's compasses). Pyxis was introduced by Nicolas-Louis ...

''). It is distinguished from all other '' Aldabrachelys'' by a massive, flattened or depressed

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

, bulging sides of the carapace, short gulars, top of the

nasal Nasal is an adjective referring to the nose, part of human or animal anatomy. It may also be shorthand for the following uses in combination: * With reference to the human nose: ** Nasal administration, a method of pharmaceutical drug delivery * ...

aperture is higher than the top of orbits, diverging quadrates, broad postorbitals, and a very large processus vomerinus dorsalis. It also had an unusually thick, strong carapace, possibly an adaptation to heavy predation. It seems to have been predominantly a grazer of meadows and wetlands.

Extinction

Material of this species has been dated to 1250–2290 years before present. It seems to have gone extinct relatively soon after the later migration of humans arrived from the mainland of Africa. Unlike its more common sister species, the abrupt giant tortoise ('' Aldabrachelys abrupta'' (also extinct)), the massive ''grandidieri'' did not seem to have succeeded in coexisting with humans for any length of time.

Ecology

''Aldabrachelys grandidieri'' (along with ''Aldabrachelys abrupta'') likely were seed dispersers of the six baobab ('' Adansonia'' spp.) species endemic to Madagascar; in an experiment, extant

Aldabra giant tortoise The Aldabra giant tortoise (''Aldabrachelys gigantea'') is a species of tortoise in the family Testudinidae and genus '' Aldabrachelys''. The species is endemic to the Seychelles, with the nominate subspecies, ''A. g. gigantea'' native to Alda ...

s (''Aldabrachelys gigantea'') readily consumed fruit of '' Adansonia rubrostipa''. Other ecological functions of giant tortoises likely included trampling and selectively consuming vegetation. It is suggested that introduced Aldabra giant tortoises could be used for restoration of these functions.

References

{{Taxonbar, from=Q4994646 Aldabrachelys Extinct animals of Madagascar Holocene extinctions Extinct turtles Fossil taxa described in 1868